The Jacks on top, right to IN, CARRIER, CVPEDAL, DIRECT and OUT. SPK has two inputs: one for an electronic music device ("IN") and another input jack for a carrier signal that can be used instead of the internal oscillator.. The "RANGE", "FREQ", "CV PEDAL" are disabled during the carrier signal jack input.

On the left side, there is an AC ADAPTER jack. Connects the DC 9 volt AC adapter with a 2.1mm barrel-type negative tip.

The SPK is one of the few ring modulator pedals available, its small size makes it even more unusual.